I tried to create a database diagramm with SQL Server 2008, but an error occurs:
Database diagram support objects cannot be installed because this database does not have a valid owner. To continue, first use the Files page of the Database Properties dialog box or the ALTER AUTHORIZATION statement to set the database owner to a valid login, then add the database diagram support objects.
Then I tried the following:
EXEC sp_dbcmptlevel 'Ariha', '90';
GO
ALTER AUTHORIZATION ON DATABASE::Ariha TO [WIN-NDKPHUPPNFL\Administrator]
GO
USE Ariha
GO
EXECUTE AS USER = N'dbo' REVERT
GO
Next erorr pops up:
Msg 15404, Level 16, State 11, Line 1 Could not obtain information about Windows NT group/user 'WIN-NDKPHUPPNFL\Administrator', error code 0x534.
The Problem is the name of the PC has changed into "DevPC" I also changed this in the update script, but still the same error 15404.
What can I do to fix this annoying error?

You should consider SQL authentication account for database ownership; then you don't have to worry about accounts coming and going, databases or instances moving to different servers, and your next PC name change. I have several systems where we use:
Or if you want to change the owner to that local Administrator account, then it should be:
Because renaming the machine to
DevPChas eliminated the local account that used to be namedWIN-ND...\Administratorand this has also invalidated the current owner of the database.If
SELECT @@SERVERNAME;is not accurate (it should sayDevPC), then in order to ensure that your server rename has taken hold within SQL Server, you may also want to issue the following: